Google has a useful new article on the Principles of Mobile Site Design. It’s based on Google/Answerlab research into how a range of users interacted with a diverse group of mobile sites. It covers homepage & site navigation, site search, commerce, form entry and usability.
However, before you go about all of this I recommend you take a step back because this presupposes you need a web site. Would users rather just use your desktop site? Might an app be better? Alternatively, consider a web app for discovery and an app for engagement.